N-(substituted)-α-(3,5-dialkyl-4-hydroxyphenyl)-α,α-disubstituted acetamides, and composition stabilized therewith

ABSTRACT

N-(substituted)-1-(piperazinealkyl)-α-(3,5-dialkyl-4-hydroxyphenyl)-.alpha.,α-disubstited acetamides, are novel compounds prepared by a novel modification of the ketoform process. The compounds are useful as stabilizers for organic materials subject to degradation in an environment in which the materials are exposed to heat, oxidation and light, particularly ultraviolet light. The compounds are especially useful in combination with known secondary stabilizers.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of Ser. No. 887,458 filedJuly 21, 1986, now abandoned which in turn is a continuation-in-part ofapplication Ser. No. 549,036 filed Nov. 7, 1983, now abandoned.

BACKGROUND OF THE INVENTION

The novel compounds of this invention areN-(substituted)α-(3,5-dialkyl-4-hydroxyphenyl)-α,α-disubstitutedacetamides in which one of the substituents on the N atom is apolysubstituted piperazine, or, a 2-piperazinone group. More correctly,the compounds are"N-(substituted)-1-(piperazinealkyl)-α-(3,5-dialkyl-4-hydroxyphenyl)-α,α-substitutedacetamides", and"N-(substituted)-1-(piperazin-2-onealkyl)-α-(3,5-dialkyl-4-hydroxyphenyl)-α,α-substitutedacetamides", either or both of which are hereinafter referred to as"3,5-DHPZNA" for brevity. These compounds have never heretofore beenmade because the tertiary alpha-carbon ("alpha-C") atom (alpha relativeto the phenyl ring) of any reactant from which such a compound mighthave been derived, is so hindered that it does not permit reaction withan amine to form the amide which, conventionally, one might expect to beformed. By "tertiary" C atom we refer to a C atom bonded only to Catoms. The distinctive feature of our compounds is that they areacetamides in which the tertiary C atom, referred to as "the alpha Catom" because it is alpha to the hydroxyphenyl ring, and also alpha tothe carbonyl C atom, is disubstituted. In other words, there is only asingle, disubstituted C atom, connecting the hydroxyphenyl ring to thecarbonyl C atom of the disubstituted acetamide.

3,5-dialkyl-4-hydroxyphenyl organic compounds, referred to as "hinderedphenols" because of the substituents on the ring C atoms flanking thering C atom carrying the hydroxyl (OH) group, have been of greatinterest for some time because of their stabilization activity. Thisinterest derived from the discovery that such compounds were excellentantioxidants, this property in turn, being related to the stability ofthe aroxyl radical represented by the typical structure ##STR1##Me=methyl wherein the "cross" substituents represent t-butyl, writtenout in greater detail on the 1-C atom. It was, until the discovery ofthe 3,5-DHPZNA radical, one of the most stable aroxyl radicals known.This prior art aroxyl radical was referred to as the "blue aroxyl" in alecture titled "The Blue Aroxyl, The First Stable Oxygen Radical, ItsDiscovery and Its Properties" given by Eugen Muller, in Lisbon on the28th of May 1973 and printed in Rev. Port. Quim. 14, 129 (1972). Theradical was referred to as "blue" because of the distinctive dark bluecrystals obtained by shaking the benzene solution of2,4,6-tri-tert.-butylphenol with potassium ferricyanide in aqueousalkali.

Since the effectiveness of hindered phenols to stabilize an organicmaterial, subject to degradation due to heat, oxygen and light, appearedto be correlated to the stability of the aroxyl radical generated byexposure of the organic material, it seemed likely that modifications inthe structure of such hindered phenols, particularly those modificationsrelating to the substituents on the 1-C atom of the phenyl ring, mightprovide aroxyl radicals which were more stable than those of the priorart. The quest appeared to devolve upon finding which particularsubstituent on the 1-C atom provided better stability of the radicalthan another substituent.

This general approach seemed to have been taken by prior workers in thefield, for example by Meier et al in U.S. Pat. No. 3,247,240, though atthe time, it can be assumed they were unaware of the existence of thearoxyl radical. Because he reacted 2,6-di-tert-butyl phenol with analpha,beta-monoolefinically unsaturated compound such as methylacrylate, he could never have substituted more than a single substituenton the alpha-C atom, that is, the alpha-C atom could never be a tertiary(that is, fully substituted) C atom. And, of course he could not haveprovided a substituted acetamide.

U.S. Pat. No. 3,338,833 to Spivack et al, issued soon thereafter,pursued the lead of Meier et al, but with substituteddialkyl-4-hydroxyphenyl amides having an alkylene (`spacer`) groupspacing the amide C atom from the phenyl ring. Again, the alpha-C atomcould never have more than a single substituent on the alpha-C atom,that is, the alpha-C atom could never be a tertiary C atom. In thereaction schemes he suggests, he specifies the reactant hydroxyphenylester or acid chloride as having a (CH₂)_(n) spacer where n is a smallwhole number, e.g. 1 or 2. Assuming one decided to impute and extend theenablement embodied in the Spivack '833 teachings to a spacer having atertiary C atom, and, chose to make a hydroxyphenyl amide spaced fromthe phenyl ring only by the tertiary C atom, one would need to haveaccess to the precursor hydroxyphenyl acid having the structure ##STR2##or its acyl derivative, wherein R¹ and R² represent alkyl, cycloalkyl,phenyl, alkyl-phenyl, naphthyl and alakylnaphthyl which serve to hinderthe OH group, and R³ and R⁴ represent alkyl substituents, which acid oracyl derivative could then be used to react with an appropriate amine.This 3,5-dialkyl-4-hydroxyphenyl substituted acetic acid, to be used asa precursor is obtained as disclosed in my U.S. Pat. No. 4,523,032 andis not a prior art compound. The corresponding ester, however, is aprior art compound and may be obtained as disclosed in 3,455,994 toKnell. I therefore reacted the ester, namely methylα-(3,5-di-t-butyl-4-hydroxyphenyl)-α-methylpropionate, which is a priorart compound, with tert-octylamine at 150°-160° C. for 4 hr but failedto find any trace of the expected amide with the tertiary alpha C atom.I then continued the reaction at 160°-170° C. for an additional 2 hr andstill failed to obtain the expected product.

To make certain this lack of reactivity was not due at least in part tothe steric hindrance of the amine group of the tert-octylamine, I choseto minimize any such effect by substituting a long straight chainalkylamine, namely octadecylamine, for the t-octylamine. I thenconducted a reaction with octadecylamine and methylα-(3,5-di-t-butyl-4-hydroxyphenyl)-α-methylbutyrate in an analogousmanner and under the same conditions of reaction as those describedimmediately hereinabove. I found the octadecylamine failed to react withthe methyl α-(3,5-di-tert.butyl-4-hydroxyphenyl)-α-methylbutyrate. Onlya trace of high mol wt material was detected by mass spectrography. Thistrace of material was identified as the dimer of the amine having a molwt of 520. The remaining material consisted of the unrected reactants.No amide with a tertiary alpha-C atom was obtained.

Later, in U.S. Pat. No. 3,787,355, Linhart et al, like Spivack '833,chose an alkylene spacer, but changed the amine believing this mightprovide more effective stabilization. Like Linhart et al, Spivack alsopursued the `bulking of the molecule` as a path to more effectivestabilization in U.S. Pat. No. 4,049,713, but retained the alkylenespacer between the ester group, or amide group, and the phenyl ring inhis hindered hydroxyphenyl alkanoates and amides. Since he had startedwith a compound which had either only one substituent on the alpha-Catom, or none, the esters he made were prepared via usual esterificationprocedures from a suitable alcohol and a carboxylic acid derivative ofthe substituted hindered phenol of interest, it is clear he could neverhave made an ester with a tertiary alpha-C atom.

In U.S. Pat. No. 4,191,683, Brunetti et al decided upon apolysubstituted piperidyl alkylamine, or a dimer or trimer of it,without linking their compounds to a hydroxyphenyl moiety, clearlyindicating that at that time, there was no suggestion that an aroxylradical might advantageously be combined with a polysubstitutedpiperidyl alkylamine, irrespective of what linkage might be used. Atleast with respect to their dimer and trimer, the emphasis was onbulking the molecule.

It is evident that the opportunity to investigate the stability of anaroxyl radical having a disubstituted alpha-C atom did not presentitself because the alpha C atom could not be disubstituted. Thisinability is borne out by the efforts of Rosenberger et al in U.S. Pat.No. 4,197,236, who were able to produce an alkyl (methyl) substituent ona tertiary C atom (see example 3) but were forced to provide an alkylenespacer between the tertiary C atom and the carbonyl C atom, to obviatethe steric hindrance and allow the reaction to proceed. When theycoupled the alpha C atom to the carbonyl C atom of the carboxyl group(see example 1), the alpha C was not disubstituted. However, theirpursuit of a "bulked-up" acetamide molecule was successful. They wereable to provide two hydroxyphenyl groups on the tertiary C atom with theexpectation of providing a more stable diradical. This was a differentapporach towards the same goal we pursued, namely finding andsynthesizing a more effective stabilizer. They opted to cope with thedestabilizing effect of the tendency of each of the two radicalsconnected to the single C atom, to form a quinone methide, butbenefitted from the bulked up molecule. We chose to use a singlehydroxyphenyl radical in which the stability was enhanced by the lonedisubstituted alpha C atom connecting the hydroxyphenyl ring to thecarbonyl C atom. Because the generation of an aroxyl radical withenhanced stability is the nexus of the activity of our compounds it isevident that they are distinct and different from the dihydroxyphenylpiperidyl compounds of the `236 patent.

Not long afterwards, in U.S. Pat. No. 4,246,198, Rosenberger et alpursued the notion of bulking the molecule even further by forming adimer or trimer after bulking the substituent on the 1-C atom of thephenyl ring. In each embodiment he provided an alkylene spacer (C_(x)H_(2x)) in which x is defined as being 0, 1, 2 or 3, optionally incombination with another such alkylene spacer (C_(y) H_(2y)). But thedisclosure of the value "0" for x was clearly accidental since there isno suggestion provided to enable one to make such a compound. Nor isthere any suggestion that such a compound, which they were earlierunable to make, might now have been made by them in this '198 patent.From the numerous examples given in the specification, it is clear thatthey did not make such a compound. This is confirmed by their statementthat in the preferred compounds they made, x an y are each either 1 or2. From the foregoing evidence of insurmountable difficulty Iencountered in my attempts to produce such a compound by any knownsynthesis other than the ketoform synthesis, it is clear that thoseknown syntheses could not have been used to make such a compound.Further, it is clear that the amine group in any of their compounds isan amine linkage which must always be a secondary amine --NH--; and theH in this linkage cannot be substituted.

Much later, in U.S. Pat. No. 4,452,884, Leppard disclosed combining ahydroxyphenyl group in which the 3,5-dialkyl substituents would producea stable aroxyl radical, except that, having recognized that "A" in hisstructure could not be a disubstituted lone C atom (the alpha C atom),he specified that A is methylene or one of several groups having pluralC atoms connecting the hydroxyphenyl group to the carbonyl C atom in hisstructure. In a subsequent patent (U.S. Pat. No. 4,518,679) Leppard etal disclosed many other piperidinyl derivatives linked to hydroxyphenylgroups with various linkages, none of which has the disubstituted alphaC atom connecting the phenyl ring to an amide carbonyl C atom. Thus itis evident that our 3,5-DHPZNA compounds are distinct and different fromthe hydroxyphenyl piperidyl compounds of both the '884 and the '679Leppard patents.

It was in the foregoing framework of related aroxyl radicals withvarying degrees of stability, measured as described hereinbelow, that Ijoined the search for a more stable aroxyl radical than the blue aroxylradical, and sought to introduce the radical into a compound which mighthave enhanced stabilization activity.

Though I subscribed to the general notion that some bulking of the 1-Csubstituent would likely produce enhancement of the stability of thebulked up aroxyl radical, relative to that of the blue aroxyl radical,there was no clear indication as to what might constitute the `proper`bulking. Many bulked up aroxyl radicals are less stable than the bluearoxyl, but there was no way of linking their activity to the lack of adisubstituted alpha-C atom. The disubstituted alpha-C atom was onlypresent on the blue aroxyl radical in which the 3- and 5-carbons alsohad substituents which contained a disubstituted C-atom, and there wasno particular reason to ascribe greater significance to the presence ofsuch a C-atom in the substituent on the 1-C atom. Nor was there anyreason to believe that an amide substituent might be about 50 times moreeffective than the blue aroxyl radical, and far more effective thanother prior art `bulking` substituents, if it could be made to include adisubstituted alpha-C atom. The optional presence of an alkylidene groupbetween the carbonyl C atom and the N atom of the carboxyamide isincidental to producing desirable "bulking" by chain extension, and hasno known theoretical relevance with respect to influencing thereactivity of the alpha C atom, and is not found to have any.

Apart from the inability to produce a disubstituted alpha C atom with amonohydroxyphenyl group in the structure, it is worth noting that, inprior art hindered phenol hydroxyphenylalkyleneyl isocyanurates whichare antioxidants having superior effectiveness, for example, Irganox1010, there are at least two C atoms in the linkage connecting the 1-Catom of the hydroxyphenyl ring to the rest of the molecule. It is thisstructure which in no small measure accounts for their effectiveness. Aswill be evident from data presented hereinafter, the compounds of ourinvention are inferior antioxidants, this property being attributable tothe disubstituted alpha C atom; but they have a surprisingly superiorstabilizing effect against degradation by ultraviolet light,attributable to the stability of the aroxyl radical formed.

Despite the activity of the 3,5-DHPZNA stabilizers of this invention,they would be of little value if they could not be made in good yields,that is, at least 50%. I found that a good yield of 3,5-DHPZNA was notobtained without one of the 3- or 5-alkyl substituents on the 3,5-DHPZNAbeing a tertiary alkyl substituent, which dictates one substituent onthe 2,6-dialkyl phenol starting material. It is much preferred to havetert.-alkyl substituents on each of the 2- and 6-carbon atoms.

SUMMARY OF THE INVENTION

It has been discovered that aN-(substituted)-1-(piperazinealkyl)-α-(3,5-dialkyl-4-hydroxyphenyl)-α,α-disubstitutedacetamide, or, aN-(substituted)-1-(piperazin-2-one-alkyl)-α-(3,5-dialkyl-4-hydroxyphenyl)-α,α-disubstitutedacetamide, either of which is referred to as "3,5-DHPZNA" herein, forbrevity, generates an exceptionally stable hindered acetamide-aroxylradical which is far more stable than the "blue aroxyl radical" derivedfrom 2,4,6-tri-t-butylphenol, which radical was heretofore adjudged thestandard of superior stability and resistance to degradation due toheat, oxygen and light, the compound having been specifically disclosedas a uv-stabilizer.

It is therefore a general object of this invention to provide a class ofhindered phenols which are disubstituted acetamides which generatesubstituted aroxyl radicals far more stable than known aroxyl radicals.The substituents on the alpha-C atom of the precursor provide such greatsteric hindrance that, when such substituents are present on a 4-hydroxyphenyl ester, used as a precursor for the formation of the desiredhindered acetamide by reaction with an appropriately substituted amine,the reaction is negated.

It has also been discovered that a hindered aroxyl amide radical whichis at least ten times more stable than the "blue aroxyl radical"heretofore deemed stable, may be generated by 3,5-DHPZNA compoundsprepared by a peculiarly effective synthesis known as the ketoformreaction. This ketoform reaction is unexpectedly well-adapted to producethe 3,5-DHPZNA compounds which we have been unable to produce by anyother synthesis known to us.

It is therefore a general object of this invention to provide anelegant, yet simple synthesis for the commercial production of3,5-DHPZNA compounds which are useful as antioxidants and lightstabilizers, particularly under elevated temperature conditions to whichorganic materials are subject in the environments in which they areused. The process comprises reacting a 2,6-dialkylphenol, a chloroformor bromoform, and an appropriately substituted aminopolysubstitutedpiperazine, or, substituted aminopolysubstituted piperazin-2-one, in thepresence of an alkali metal hydroxide to form the desired 3,5-DHPZNA.

It is a specific object of this invention to provide a 3,5-DHPZNA whichgenerates a hindered carboxyamide aroxyl radical which is so stable thata very small amount of the hindered aroxyl acetamide radical, derivedfrom a compound of this invention which compound is present in the rangefrom about 0.01 to about 1 phr (part per hundred parts organic materialto be stabilized), provides satisfactory stability of the materialcontaining the compound.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

This search for a more stable aroxyl radical was spurred by the notionthat the steric configuration of the alpha-C atom connecting the 1-Catom of the phenyl ring and the carbonyl C atom, peculiarly enhanced thestability of an aroxyl radical. In due course, this search led toamides, and more specifically substituted acetamides, which we hoped,might further enhance the stability of the aroxyl radical. Except, asstated hereinbefore, there was no known way of overcoming the sterichindrance which frustrated the formation of the 3,5-DHPZNA we desired tomake and test.

It was only because of the earlier discovery of the ketoform reaction(U.S. Pat. No. 4,466,915 to John T. Lai) for the preparation of a2-keto-1,4-diazacycloalkane, that we resorted to the use of a ketone andan amine in the presence of a haloform and alkali in a synthesis for the3,5-DHPZNA. We were happily surprised to find that, despite the lack ofsimilarity between the formation (by cyclization) of a2-keto-1,4-diazacycloalkane, and the attack of a 1-C atom of a phenylring, the combination of an appropriate ketone and amine in the presenceof chloroform or bromoform and an alkali, successfully introduced asubsituent with a tertiary alpha-C atom on the 1-C atom of the phenylring, and generated the substituted acetamide.

Though all hindered phenols (referring to the hindrance of the OH group)have a stabilizing effect, the search for a more effective aroxylradical requires testing of the radicals derived from a wide option ofsubstituents on the 1-carbon atom of the phenyl ring. Such testing isdone by measuring the half-life of each radical. The half life ("t 1/2")is the time it takes for the aroxyl radical to lose 50% of itsintensity, as evidenced by the height of the peak registered in anElectron Spin Resonance (ESR) Spectroscope. To make the measurement, 50ml toluene with potassium ferricyanide and aqueous alkali are placed ina 250 ml three-necked flask equipped with a magnetic stirrer. Thesolution turns orange. The hindered phenol being tested is dissolved, in50 ml toluene, and the solution added, a little at a time over about 45min, to the flask. The solution turns blue-green and is stirred undernitrogen for 2 hr. A 10 ml sample is withdrawn and diluted to 100 mlwith toluene to provide a 10⁻³ molar concentration. It is dried byadding Mg₂ (SO₄)₂, then filtered. The filtrate in a tube is then placedin the ESR 'scope and an initial reading is made. Then, afterpreselected intervals, usually 0.5 hr, the peak height of the sample isagain measured, and the procedure repeated until a peak one-half theheight of the original peak is registered. The combined intervals oftime after which this last measurement was made is defined as thehalf-life of the radical. A precise half-life is obtained by plottingpeak height vs. time.

Representative prior art compounds were prepared and tested followingthe foregoing procedures. Such compounds were chosen because of (i) thespecific nature of substitution on the alpha-C atom, and (ii) the"bulking effect" provided by an unsubstituted, or, a single substituenton the alpha-C atom in the acetamide, or, by a "spacer" as inβ-(3,5-di-t-butyl-4-hydroxyphenyl)-propanamide.

The criticality of the substituents on the alpha-C atom of the acetamideis best demonstrated by comparing three 3,5-DPHA compounds differingonly in the linkage connecting the hydroxyphenyl ring to the carbonyl Catom.

In the prior art compounds herebelow, as in the substituted acetamidesof this invention, no distinction is made between the effect ofsubstituents on the N atoms, to the extent that each N atom is tertiaryand di-alkyl-substituted, except that (i) compound A, disclosed inSpivack '833 has only a single methyl substituent on the alpha-C atom;(ii) compound B disclosed in Spivack '713 has no substituent on thealpha-C atom; and (iii) compound C disclosed in Linhart '355 has anunsubstituted alpha-C atom, but the extra C atom is in the dimethylenespacer connecting the hydroxyphenyl ring to the carbonyl C atom. Thiscompound C differs from those disclosed in U.S. Pat. No. Re. 27,004 toMeier, in that the alpha-C atom in the latler may have a singlesubstituent.

The results for the stability of the aroxyl radicals listed herebelow(the crosses represent t-butyl substituents) are derived from such priorart compounds by oxidation with potassium ferricyanide in aqueousalkali. ##STR3## Half life "t 1/2" of each of the above is less than 0.5hr.

Each of the foregoing prior art radicals is less stable than the bluearoxyl radical which has a half-life of 0.5 hr, deemed very good.

By comparison with prior art aroxyl radicals, those derived from3,5-DHPZNA compounds of this invention are many times more stable, asevidenced by the following measurement of the stability of a particular3,5-DHPZNA aroxyl radical by the procedure described hereinabove. Theparticular compound (prepared as in example 1) tested has methylsubstituents on the alpha-C atom, and the 1,4-diaza ring is apolysubstituted 2-keto-piperazinone.

    ______________________________________                                        Compound 1 (made in example 1 herebelow)                                                                 Half-life                                          ______________________________________                                        N--isopropyl-N--[2-(2-keto-3,3,5,5-tetramethyl-                                                          >30 hr                                             1-piperazinyl)ethyl]-2-(3,5-di- .sub.-t-butyl-4-                              hydroxyphenyl)-2-methyl propanamide                                           ______________________________________                                    

From the foregoing result it is evident that the aroxyl radical derivedfrom the dimethyl-substituted alpha-C atom of a specific compound ofthis invention is unexpectedly over sixty times more stable than priorart aroxyl radicals derived from prior art compounds which do not have adisubstituted alpha-C atom. It is not expected that the substituents onthe N atom have comparable influence on the stability of the aroxylradical because of their relatively greater distance.

Test samples are prepared by mixing a predetermined amount of stabilizerinto PP in a Brabender Plasticorder fitted with a Cam-Head (mixingchamber). The PP is first masticated for 1.5 min at 190° C. Thestabilizer is then added followed by 3 min additional mixing. Thestabilized mass of PP is removed and pressed into 20 ml thick sheetsfrom which 1"×1" plaques are cut for oven aging. Type C (3"×0.125" wide)tensile bars are cut for UV stability tests.

Thermal oxidative stability (oven aging) is measured by aging thesamples in triplicate in an air-circulating oven at 125° C. The time tofailure, indicated by crumbling of the sample when rubbed between thefingers of one hand, was recorded as number of days to failure. Eachsample contained 0.1 phr (part of stabilizer per 100 parts of PP).

Samples containing 0.1 phr of stabilizer to be tested are also testedfor uv-stability, i.e. resistance to degradation by ultraviolet light.The samples were tested in an Atlas Xenon Weatherometer, Model No.65-WR, equipped with a 6500 watt Xenon burner tube in accordance withASTM D 2565-79-A. The black panel temperature was 60° C. The sampleswere subjected to an 18-min water cycle every 2 hr. The time in hrs to a50% loss in tensile strength was determined. For a control, and standardfor comparison, a sample containing no stabilizer is also tested.

The comparative effectiveness of the stabilization to degradation, byuv-light, provided by compounds having (i) no substituent on the alpha-Catom, (ii) only one substituent on the alpha-C atom, and (iii) twosubstituents on the alpha-C atom, but keeping the substituents on the Natom the same, is demonstrated by incorporating each, at various levelsof concentration, in PP, and testing as stated immediately hereinabove.

    ______________________________________                                                  phr                                                                                          0.1                                                  Compound    0.05         hours   0.2                                          ______________________________________                                         ##STR4##   360          510     600                                           ##STR5##   450          615     785                                           ##STR6##   610          820     970                                          ______________________________________                                    

The effectiveness of the 3,5-DHPZNA compounds as stabilizers was testedin an analogous manner by incorporating them in polypropylene (PP) testsamples, exposing the samples to a polymer-degrading level of heat andlight, and recording the time after which a sample loses 50% of itstensile strength. The test results set forth hereafter are evidence thatsamples stabilized with a wide variety of substituents on thedisubstituted alpha-C atom exhibit excellent stability to uv light.

The foregoing compound of example 1 of this invention is representativeof aN-substituted-N-polysubstituted-1,4-diaza-2-(3,5-dialkyl-4-hydroxyphenyl)-2,2-substitutedacetamide, represented by the structure ##STR7## wherein R¹, R² and R⁵each represent hydrogen, C₁ -C₁₂ alkyl, phenyl, naphthyl, C₄ -C₁₂cycloalkyl, and, alkyl-substituted cycloalkyl, phenyl and naphthyl, eachalkyl substituent being C₁ -C₈, and at least one of R¹ and R² is t-C₄-C₁₂ alkyl;

R³ and R⁴ independently represent C₁ -C₁₈ alkyl, and C₅ -C₁₂ cycloalkyl,phenyl and naphthyl, and, alkyl-substituted cycloalkyl, phenyl andnaphthyl, each alkkyl substituent being C₁ -C₈, and, when togethercyclized, R³ with R⁴ may represent C₄ -C₁₂ cycloalkyl, and C₁ -C₈alkyl-substituted cycloalkyl;

R⁶, R⁷, R⁸ and R⁹ each represent C₁ -C₁₂ alkyl, or, when togethercyclized, R⁶ with R⁷, and R⁸ with R⁹, may represent C₄ -C₁₂ cycloalkyl,and C₁ -C₈ alkyl-substituted cycloalkyl;

R¹⁰ is selected from the group consisting of hydrogen, C₁ -C₈ alkyl and##STR8## wherein R¹³ represent hydrogen, C₁ -C₁₈ alkyl or alkenyl,phenyl or naphthyl;

R¹¹ and R¹² independently represent hydrogen and C₁ -C₁₈ alkyl;

n is an integer in the range from 1 to about 8; and,

Y represents H₂ when the diaza ring is piperazinyl, and O when the diazaring represents piperazine-2-one.

It will be appreciated that when R₁₀ is to be acyl, it is introduced byan acylation step after formation of the 3,5-DHPZNA in which there is nosubstituent on the N⁴ atom of the diazacycloalkane ring.

The process for preparing the foregoing 3,5-DHPZNA compounds comprisesreacting a 2,6-dialkylphenol with at least an equimolar quantities of analiphatic, cycloaliphatic or alkaryl ketone and a4-amino-polysubstituted piperazine or 4-amino-polysubstitutedpiperazin-2-one in the presence of an alkali metal hydroxide, preferablyat a temperature in the range from about -10° C. to about 50° C.

The 2,6-dialkylphenol reactant is represented by the structure ##STR9##wherein R¹ and R² have the same connotations set forth hereinabove.Typical such reactants include 2-methyl-6-t-butylphenol,2-ethyl-6-t-butylphenol, 2-propyl-6-t-butylphenol,2-isopropyl-6-t-butylphenol, 2-n-butyl-6-t-butylphenol,2,6-di-t-butylphenol, 2-n-amyl-6-t-butylphenol,2-isoamyl-6-t-butylphenol, 2-heptyl-6-t-butylphenol,2-isooctyl-6-t-butylphenol, 2-isopropyl-6-methylphenol,2-n-butyl-6-isopropylphenol, 2-isopropyl-6-ethylphenol,2-n-butyl-6-iosopropylphenol, 2-isoamyl-6-ethylphenol,2-isoamyl-6-methylphenol, 2-isooctyl-6-methylphenol,2-isooctyl-6-ethylphenol, 2-isooctyl-6-n-propylphenol,2-isooctyl-6-n-hexylphenol, 2,6-di-(2-phenylpropyl)phenol,2-methyl-6-(2-phenylpropyl)phenol, etc. the common being most preferred.

The 4-amino-polysubstituted piperazin-2-ones are N-substituted cyclicalkyleneimines represented by the structure ##STR10## wherein R⁵, R⁶,R⁷, R⁸, R⁹ and R¹⁰ have the same connotation as that given hereinbefore.Two or more of the 4-amino-polysubstituted piperazinone moieties may bepresent on a single molecule, for example, when the moiety is asubstituent in each of the two primary amine groups of an alkanediamine; or, of a triamine or tetramine. Preferred substituents are C₁-C₈ alkyl, branched or unbranched, and, preferred cyclic substituentsare C₃ -C₆ cycloalkyl in compounds exemplified by4-methylamino-2,2,6,6-tetramethylpiperazin-2-one;4-ethylamino-2,2,6,6-tetramethylpiperazin-2-one;4-butylamino-2,2,6,6-tetramethyl-piperazin-2-one;N,N'-bis-(2,2,6,6-tetramethyl-4-piperazin-2-one)-1,6-hexanediamine, andthe like.

Corresponding structurally analogous polysubstituted piperazines arerepresented by the structure ##STR11## and are prepared from theforegoing piperazin-2-one by reduction, for example with lithiumaluminum hydride (LiAlH₄) in refluxing tetrahydrofuran (THF). Typicalpolysubstituted piperazinesare4-methylamino-2,2,6,6-tetramethylpiperazine;4-ethylamino-2,2,6,6-tetramethylpiperazine;4-butylamino-2,2,6,6-tetramethyl-piperazine;N,N'-bis(2,2,6,6-tetramethyl-4-piperazinyl)-1,6-hexanediamine, and thelike.

The 3,5-DHPZNA is then produced by the ketoform reaction. As before, atleast a stoichiometric amount of the 4-amino-polysubstituted piperazineis used, relative to the amount of 2,6-dialkylphenol, an excess of aminebeing preferred for good yields. Most preferred is up to a four-foldexcess.

The ketone reactant may be a dialkylketone, a cycloalkanone, oralkylcycloalkanone, represented by the structure ##STR12## wherein, R³and R⁴ are independently selected from C₁ -C₈ alkyl, preferably acetone,methyl ethyl ketone, methyl n-propyl ketone, diethyl ketone, 2-hexanone,3-hexanone, di-n-propyl ketone, 2-octanone, methyl isopropyl ketone, andthe like; or, when together cyclized, represent C₅ -C₁₂ cycloalkyl,preferably cyclobutanone, cyclopentanone, cyclohexanone, cycloheptanone,cyclooctanone, cyclodecanone, methylcyclopentanone, methylcyclohexanone,dicyclohexyl ketone, and C₁ -C₄ alkyl alkaryl ketones preferablyacetophenone, o-methoxyacetophenone, p-chloroacetophenone, and the like.

It is preferred to use a stoichiometric excess of the ketone, sufficientto provide a solution for the organic reactants, but a greater thanten-fold excess serves no useful purpose. If a ketone solution isunnecesssary, less than a two-fold excess is generally found adequate.

Chloroform and bromoform may be interchangeably used, though the former,used in a slight, up to 50% molar excess relative to the 2.6-dialkylphenol, is preferred. A larger excess greater than 1.5:1.0 simplyinterferes with work-up of the reaction mass.

The alkali metal hydroxide, typically sodium hydroxide or potassiumhydroxide, is preferably used as a powder, or as a conc. aqueoussolution, also in molar excess relative to the 2,6-dialkyl phenol,preferably from about a four- to eight-fold excess. Use of less than afour-fold excess will reduce the yield of product.

Although a catalyst may be used, it is not essential, and it ispreferred not to use one. When used, preferred catalysts are the oniumsalts, that is, quarternary compounds of ions derived from Group VA andVIA elements, which compounds have the formula (R'₄ Y')⁺ X⁻ wherein R'is a monovalent hydrocarbon radical including alkyl, aryl, alkaryl,cycloalkyl and like radicals, Y' is phosphorus or nitrogen, and X is ahalide, hydrogen sulfate, or like ions. Benzyltriethylammonium chloride(BTAC) has been found useful when used in an amount in the range fromabout 0.01 mole to about 0.1 mole of BTAC per mole of 2,6-dialkylphenol.Other catalysts useful in the process include tetraalkyl ammonium saltssuch as tetrabutyl ammonium bromide, tetrabutyl ammonium hydrogensulfate, methyltrioctyl ammonium chloride, tetraalkyl phosphonium saltssuch as tetrabutyl phosphonium bromide, cetyltributyl phosphoniumbromide, and the like.

A solvent for the organic reactants may be any polar organic solvent,and the ketone reactant itself may also function as the solvent.Commercially available solvents which are useful are methylene chloride,tetrahydrofuran, diethyl ether, dibutyl ether, dimethyl sulfone,1,4-dioxane, carbon tetrachloride, toluene, and the like. The amount ofsolvent used is not critical, a 5 to 20-fold molar excess relative tothe 2,6-dialkylphenol, and preferably a 7.5 to 15-fold excess, beinggenerally used.

While the order of addition of the reactants is not narrowly critical,it is preferred that the alkali metal hydroxide be added last, and overa period of time, to control the reaction which is exothermic, andmaintain the temperature below about 30° C., more preferably below about10° C. The reaction time will vary from about 5 to about 15 hr for smallquantities of product.

The 3,5-DHPZNA product is readily isolated from the reaction mass byfiltration, and washing the filtrate with aqueous inorganic acid,typically HCl or H₂ SO₄. The filtrate is dried with a dessicant such assodium sulfate, then heated to dryness. The product obtained may berecrystallized from a solvent if greater purity is desired.

The structure of the 3,5-DHPZNA product is confirmed by elementalanalysis for carbon and hydrogen, and infrared (IR) and nuclear magneticresonance (NMR) spectra. Molecular weights were determined and confirmedby field desorption mass spectra (FD/MS).

EXAMPLE 1

A. Preparation ofN-isopropyl-N-[2-(2-keto-3,3,5,5-tetramethyl-1-piperazinyl)ethyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methyl-propanamiderepresented by the structure ##STR13## M=methyl

0.1 Mole of 2,6-di-t-butylphenol, 1.0 mole of acetone, 0.15 mole ofchloroform, and 0.1 mole ofN'-(2-isopropylaminoethyl-3,3,5,5-tetramethyl-2-piperazinone are addedto a reactor and mixed by stirring while being cooled in a circulatingice-cold bath. 0.5 mole of powdered NaOH is slowly added over a periodof 1 hr. The reaction mixture is stirred at 10° C. overnight. Thereaction mix from the reactor is filtered, the solid residue washed withmethylene chloride, and the wash added to the filtrate. The filtrate iswashed with 50 ml of 4N hydrochloric acid, 50 ml of 5% sodium carbonate,then dried over sodium sulfate. The filtrate is evaporated to drynessand the dried product is washed with hexane. The resulting amide is awhite solid with a melting point of 165°-169° C. and a molecular weightof 515. By elemental analysis it is determined that the amide contained72.43% carbon (72.19% calculated), 10.26% hydrogen (calculated 10.36 %)and 8.02% nitrogen (calculated 8.15%).

B. N'-(2-isopropylaminoethyl-3,3,5,5-tetramethyl-2-piperazinone isreduced to yield the corresponding piperazine which is then reacted in amanner analogous to that described hereinabove in 1A, to produceN-isopropyl-N-[2-(3,3,5,5-tetramethyl-1-piperazinyl)ethyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methyl-propanamide.

EXAMPLE 2

A. Preparation ofN-[1-(2-keto-3,3,5,5-tetramethyl-1-piperazinyl-2-methyl-2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methyl-propanamiderepresented by the structure ##STR14##

0.1 mol of imino-bis-(2-amino-2-methyl-1 propane), 0.15 mol chloroformand 2.0 mols of acetone were placed in a 3-neck flask equipped with athermometer, a mechanical stirrer, cooling means and an addition funnel.The mixture is kept cool in a circulating ice-bath, while 0.5 mol- ofNaOH beads are added in small portions to keep the reaction temperaturebelow 10° C. After the addition, the reaction is stirred under nitrogenuntil a GC (gas chromatographic) analysis of a sample shows the reactionof the amine is substantially complete. 0.14 mols of chloroform and 0.1mole of 2.6-di-t-butylphenol are added, followed by 0.5 mole of NaOHbeads in portions to keep the temperature below 10° C. The mixture isstirred at 10° C. overnight. The mass is concentrated in a rotaryevaporator to remove solvents and low boilers and stirred in ahexanes-water mixture. The solid is collected and washed with hexanesand water. The yield is about 70% after drying. The substitutedpropanamide is recrystallized from 70% ethanol with a few drops of 85%hydrazine to yield white crystals. The melting point is 145°-8° C.

B. In a manner analogous to that described hereinabove in 1B, thecorresponding piperazine is reacted to produceN-[1-(3,3,5,5-tetramethyl-1-piperazinyl-2-methyl-2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methyl-propanamide.

EXAMPLE 3

A. Preparation ofN-[1-(2-keto-3,5,5-trimethyl-3-ethyl-1-piperazinyl-2-methyl-2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methyl-butanamiderepresented by the structure ##STR15## E=ethyl

In a manner analogous described in example 2 hereinabove, but replacingthe ketone used therein with 2 mols of butanone, a substitutedbutanamide is obtained which is represented by the structure immediatelyhereinabove, and has a melting point of 126°-8° C.

B. In a manner analogous to that described hereinabove in 1B, thecorresponding piperazine is reacted to produceN-[1-(3,5,5-trimethyl-3-ethyl-1-piperazinyl-2-methyl-2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methylbutanamide.

EXAMPLE 4

A. Preparation ofN-[1-(2-keto-3,3-pentamethylene-5,5-dimethyl-1-piperazinyl)-2-methyl-2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethyleneacetamide represented by the structure ##STR16##

In a manner analogous described in example 2 hereinabove, but replacingthe ketone used therein with 2 mols of cyclohexanone, a substitutedacetamide is obtained which is represented by the structuree immediatelyhereinabove, and has a melting point of 179°-182° C.

B. In a manner analogous to that described hereinabove in 1B, thecorresponding piperazine is reacted to produceN-[1-(3,3-pentamethylene-5,5-dimethyl-1-piperazinyl)-2-methyl-2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethyleneacetamide.

EXAMPLE 5

A. Preparation ofN-[1-(2-keto-3,3,5,5-tetramethyl-1-piperazinyl-2-methyl2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethyleneacetamide represented by the structure ##STR17##

In a manner analogous to that described in example 2 hereinabove, butreplacing the substituted piperazinone used therein with 0.1 mol of N¹-(2-amino-2-methyl-1-propyl)-3,3,5,5-tetramethyl-2-piperazinone, thesubstituted acetamide represented by the structure immediatelyhereinabove is obtained as an off-white colored powder byrecrystallization from hexanes and has a melting point of 125°-130° C.

B. In a manner analogous to that described hereinabove in 1B, thecorresponding piperazine is reacted to produceN-[1-(3,3,5,5-tetramethyl-1-piperazinyl-2-methyl2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethyleneacetamide.

EXAMPLE 6

A. Preparation ofN-cyclohexyl-N-[2-(2-keto-3,3,5,5-tetramethyl-1-piperazinylethyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethylene acetamiderepresented by the structure ##STR18##

In a manner analogous described in example 2 hereinabove, but replacingthe substituted piperazinone used therein with 0.1 mol of N¹-(2-cyclohexylaminoethyl)-3,3,5,5-tetramethyl-2-piperazinone, thesubstituted acetamide represented by the structure immediatelyhereinabove is obtained as an off-white colored powder byrecrystallization from hexanes and has a melting point of 60° C.

B. In a manner analogous to that described hereinabove in 1B, thecorresponding piperazine is reacted to produceN-cyclohexyl-N-[2-(3,3,5,5-tetramethyl-1-piperazinylethyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethylene acetamide.

EXAMPLE 7

A. Preparation ofN-cyclohexyl-N-[3-(2-keto-3,3,5,5-tetramethyl-1-piperazinylpropyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethylene acetamiderepresented by the structure ##STR19##

In a manner analogous described in example 2 hereinabove, but replacingthe substituted piperazinone used therein with 0.1 mol of N¹-(2-cyclohexylamino-1-propyl)-3,3,5,5-tetramethyl-2-piperazinone, thesubstituted acetamide represented by the structure immediatelyhereinabove is obtained as a powder by recrystallization from hexanes,and has a melting point of 60° C.

B. In a manner analogous to that described hereinabove in 1B, thecorresponding piperazine is reacted to produceN-cyclohexyl-N-[3-(3,3,5,5-tetramethyl-1-piperazinylpropyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethylene acetamide.

EXAMPLE 8

A. Preparation ofN-cyclohexyl-N-[3-(2-keto-3,3,5,5-tetramethyl-1-piperazinyl-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methylpropanamide represented by the structure ##STR20##

In a manner analogous to that described in example 2 hereinabove, butreplacing the substituted piperazinone used therein with 0.1 mol of N¹-(2-amino-2-methyl-1-propyl)-3,3,5,5-tetramethyl-2-piperazinone, thesubstituted acetamide represented by the structure immediatelyhereinabove is obtained as a powder by recrystallization of hexanes andhas a melting point of 172°-174° C.

B. In a manner analogous to that described hereinabove in 1B, thecorresponding piperazine is reacted to produceN-cyclohexyl-N-[3-(3,3,5,5-tetramethyl-1-piperazinylpropyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methylpropanamide.

EXAMPLE 9

A. Preparation ofN-cyclohexyl-N-[3-(2-keto-3,3,5,5-tetramethyl-1-piperazinyl-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methylbutanamide represented by the structure ##STR21##

In a manner analogous to that described in example 2 hereinabove, butreplacing the ketone used therein with 2 mols of 2-butanone, asubstituted acetamide is obtained which is represented by the structureimmediately hereinabove, and has a melting point of 118°-121° C.

B. In a manner analogous to that described hereinabove in 1B, thecorresponding piperazine is reacted to produceN-cyclohexyl-N-[3-(3,3,5,5-tetramethyl-1-piperazinylpropyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methylbutanamide.

To demonstrate the stabilizing activity of the 3,5-DHPZNA compounds,test samples of polypropylene in which each of the compounds ishomogeneously dispersed, are prepared as described hereinbefore.

The following results were obtained for thermal/oxidative stability at125° C., given in "days to failure" judged by crumbling, forcompositions stabilized with specific 3,5-DHPZNA stabilizers:

    ______________________________________                                                                 Days                                                 ______________________________________                                        Control (blank)            2                                                  Compound 1A (made in example 1A herebelow)                                    N--isopropyl-N--[2-(2-keto-3,3,5,5-tetramethyl-                                                          9                                                  1-piperazinyl)ethyl]-2-(3,5-di- .sub.-t-butyl-4-                              hydroxyphenyl)-2-methyl propanamide                                           ______________________________________                                    

It is evident from the foregoing that the thermal/oxidative stabilizingactivity of the 3,5-DHPZNA compounds is lower than that of commerciallyavailable materials with two unsubstituted carbon atoms in the link tothe hydroxyphenyl ring, such astris-[3,5-di-t-butyl-4-hydroxyphenyl]-isocyanurate, but 3,5-DHPZNA docontribute to the overall stabilizing power of the compounds and aresurprisingly effective against degradation by ultraviolet light.

Samples of PP containing the foregoing stabilizers were also tested foruv stabilizing activity, in the manner described hereinabove. The timeto degradation severe enough to cause a 50% loss of tensile strength, isgiven in hrs. As before, the control was a blank containing nostabilizer.

    ______________________________________                                                                 hrs.                                                 ______________________________________                                        Control (blank)             220                                               Compound 1A (made in example 1A herebelow)                                    N--isopropyl-N--[2-(2-keto-3,3,5,5-tetramethyl-                                                          1280                                               1-piperazinyl)ethyl]-2-(3,5-di- .sub.-t-butyl-4-                              hydroxyphenyl)-2-methyl propanamide                                           ______________________________________                                    

The 3,5-DHPZNA stabilizers of this invention provide an exceptionalcombination of heat stability and resistance to uv degradation when usedin polyolefin resins. They aree especially effective stabilizers inα-monoolefin homopolymers and copolymers, wherein the α-monoolefincontains 2 to about 8 carbon atoms. High and low density polyethylene,isotactic and atactic polypropylene, polyisobutylene, andpoly(4-methyl-1-pentene) have excellent resistance to heat and oxygenwhen stabilzed with combinations of stabilizers of this invention.Ethylene-propylene copolymers and ethylene-propylene terpolymers,generally containing less than about 10 percent by weight of one or moremonomers containing multiple unsaturation provided by, for example,1,4-hexadiene, dimethyl-1,4,9-decatriene, dicyclopentadiene, vinylnorbornene, ethylidene norbornene, and the like, also provide excellentaging using conbinations of the stabilizers.

By "combination of stabilizers of this invention" I refer not only tocombinations of the 3,5-DHPZNA stabilizers which might be more effectivethan a single 3,5-DHPZNA stabilizer, but also more particularly, tocombinations of a 3,5-DHPZNA stabilizer with known stabilizers, some ofwhich are identified hereafter, for a specific organic material soughtto be stabilized in the environment in which it is to be used.

Organic materials which may be stabilized against uv light, thermal andoxidative degradation, include copolymers of butadiene with acrylicacid, alkyl acrylates or methacrylates, polyisoprene, polychloroprene,and the like; polyurethanes; vinyl polymers known as PVC resins such aspolyvinyl chloride, copolymers of vinyl chloride with vinylidenechloride, copolymers of vinyl halide with butadiene, styrene, vinylesters, and the like; polyamides such as those derived from the reactionof hexamethylene diamine with adipic or sebacic acid; epoxy resins suchas those obtained from the condensation of epichlorohydrin withbisphenols, and the like; ABS resins, polystyrene, polyacrylonitrile,polymethacrylates, polycarbonates, varnish, phenol-formaldehyde resins,polyepoxides, polyesters, and polyolefin homo- and copolymers such aspolyethylene, polypropylene, ethylene-propylene polymers,ethylene-propylenediamine polymers, ethylene vinyl acetate polymers andthe like. The 3,5-DHPZNA stabilizers can also be used to stabilizemixtures and blends of oligomeric materials such as ABS resin blends,PVC and polymethacrylate blends, and blends of homopolymers andcopolymers such as blends of polypropylene in EPDM polymers.

Most particularly, the 3,5-DHPZNA stabilizers are especially useful asuv-light stabilizers for synthetic resinous materials used in the formof fibers, or in thermoformed shaped articles which are at leastpartially permeable to visible light, and particularly for thosearticles which are transparent thereto, such as those made frompolyvinylaromatics and polyolefins.

The excellent compatibility of 3,5-DHPZNAs with phenolic antioxidantsallows the latter to be used as secondary stabilizers in a mixture whichenhances the stability of the composition in which the mixture is used,with predictably good results. When so used, the phenolic AOs preferablyrange from about 0.1 to about 5 phr of the material to be stabilized.Such hindered phenol AOs are 2,6-di-t-butyl-paracresol;2,2'-methylene-bis(6-t-butyl-phenol);2,2'-thiosbis(4-methyl-6-t-butyl-phenol);2,2'-methylene-bis(6-t-butyl-4-ethyl-phenol);4,4'-butylidene-bis(6-t-butyl-m-cresol);2-(4-hydroxy-3,5-di-t-butylanilino)-4,6-bis(octylthio)-1,3,5-triazine;benzenepropanoic acid,3,5-bis(1,1-dimethylethyl)-4-hydroxy-,(2,4,6-trioxo-1,3,5-triazine-1,3,5(2H,4H,6H)-triyl)tri-2,1-ethanediylester (Goodrite®3125); tetrakis[methylene3-(3',5'-di-t-butyl-4'-hydroxyphenyl)propionate]methane; andparticularly commercially available antioxidants such as Irganox 1010,1035, 1076 and 1093.

Of the other types of AOs used, are the phosphite,o-hydroxy-benzophenone, benzotriazole, and sulfide AOs, the first threegeneric types having the effect of boosting the uv stability of thecomposition most unexpectedly.

The 3,5-DHPZNAs are found to be highly effective stabilizers inpolpropylene fibers, as evidenced by the test results set forth belowfor samples in which the 3,5-DHPZNA was combined with 0.1 hr calciumstearate, 0.1 phr of tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurateand blended into 100 parts of Profax PP. The stabilized PP is pelletizedand spun into fiber which is tested in a Weather-O-Meter for hours tofailure.

    ______________________________________                                                                  Hrs.                                                ______________________________________                                        Control sample with tris(3,5-di- .sub.-t-butyl-4-                                                         260                                               hydroxybenzyl)isocyanurate (0.1 phr)                                          Test sample 3, with                                                           N--[1-(2-keto-3,3,5,5-tetramethyl-1-piperazinyl-                                                          1080                                              2-methyl-2-propyl]-2-(3,5-di- .sub.-t-butyl-4-hydroxy-                        phenyl)-2-methyl-propanamide                                                  Test sample 4, with                                                           N--[1-(2-keto-3,3-pentamethylene-5,5-dimethyl-1-                                                          980                                               piperazinyl)-2-methyl-2-propyl]-2-(3,5-di- .sub.-t-butyl-                     4-hydroxyphenyl)-2,2-pentamethylene acetamide                                 Test sample 5, with                                                           N--cyclohexyl-N--[3-(2-keto-3,3,5,5-tetramethyl-1-                                                        530                                               piperazinyl-propyl]-2-(3,5-di- .sub.-t-butyl-4-hydroxy-                       phenyl)-2-methyl propanamide                                                  ______________________________________                                    

The 3,5-DHPZNA stabilizers are particularly effective with secondarystabilizers in polypropylene (PP), as evidenced by the following testson PP samples in which from about 0.05 phr to 5 phr of the 3,5-DHPZNAbeing tested, and from 0.05 phr to 5 phr of a secondary stabilizer,preferably with a processing aid, and/or lubricant, such as calciumstearate, are mixed into the PP until homogeneously distributed.

    ______________________________________                                                                  Hrs.                                                ______________________________________                                        Control (blank) -undecane 2,2',2"-tris[3(3,5-di- .sub.-t-butyl-4-                                           340                                             hydroxyphenyl)propionyloxy]ethyl isocyanurate                                 (0.05 phr)                                                                    Test sample 1                                                                 N--isopropyl-N--[2-(2-keto-3,3,5,5-tetramethyl-                                                           >2000                                             1-piperazinyl)ethyl]-2-(3,5-di- .sub.-t-butyl-4-                              hydroxyphenyl)-2-methyl propanamide, (0.05 phr)                               and                                                                           1,1'-(1,2-ethanediyl)bis(3,3,5,5-tetramethyl-                                 1-piperazinone, (0.05 phr)                                                    and                                                                           2,2',2"-tris[3(3,5-di- .sub.-t-butyl-4-hydroxy-                               phenyl)propionyloxy]ethyl isocyanurate (0.05 phr)                             Test sample 2                                                                 N--isopropyl-N--[2-(2-keto-3,3,5,5-tetramethyl-                                                           >2000                                             1-piperazinyl)ethyl]-2-(3,5-di- .sub.-t-butyl-4-                              hydroxyphenyl)-2-methyl propanamide, (0.125 phr)                              and                                                                           3,9-bis(octadecyloxy)-2,4,8,10-teraoxa-3,9-diphospha-                         spiro[5,5,5]-undecane (0.125 phr)                                             and                                                                           2,2',2"-tris[3(3,5-di- .sub.-t-butyl-4-hydroxy-                               phenyl)propionyloxy]ethyl isocyanurate (0.05 phr)                             ______________________________________                                    

Certain 3,5-DHPZNAs are found to be more effective as uv lightstabilizers than as antioxidants, and others are found to havesubstantially better antioxidant activity. Therefore, a combination of3,5-DHPZNAs may be used. Even more effective than a combination of3,5-DHPZNAs is a combination of a 3,5-DHPZNA with another stabilizer,sometimes referred to as a secondary stabilizer, selected fromdiphosphites, triaryl phosphites and o-hydroxy-benzophenones or2-hydroxyphenylbenzotriazole compounds, known to be effectivestabilizers for specific synthetic resinous materials, particularlythose derived from an acyclic hydrocarbon with single unsaturation.

A stabilized composition of matter is most preferably

(a) a polymer which is derived from a singly unsaturated acyclichydrocarbon, or mixtures or copolymers thereof, in which is dispersed

(b) from 0.05 to 5 parts per hundred parts by weight of the polymer, ofa mixture of

(i) the 3,5-DHPZNA, and,

(ii) from 0.05 to about 5 phr of another stabilizer selected from thegroup consisting of a (a) bis-(dialkylphenyl)pentaerythritoldiphosphite, (b) triarylphosphite, (c) o-hydroxy-benzophenone, and (d) a2-hydroxyphenylbenzotriazole,

said diphosphite represented by the structure ##STR22## wherein R¹⁴ isC₃ -C₂₄ alkyl, or di-(C₃ -C₉)alkylphenyl;

said triarylphosphite represented by the structure ##STR23## wherein R¹⁵represents t-butyl, 1,1-dimethylpropyl, cyclohexyl or phenyl, and one ofR¹⁶ and R¹⁷ is hydrogen and the other is hydrogen, methyl, t-butyl,1,1-dimethylpropyl, cyclohexyl or phenyl;

said o-hydroxy-benzophenone represented by the structure ##STR24##wherein R¹⁸ is C₁ -C₂₄ alkyl, and,

said 2-hydroxyphenylbenzotriazole represented by the structure,##STR25## wherein R¹⁹ is lower alkyl or halogen (preferably chlorine);R²⁰ is lower alkyl, halogen (preferably chlorine), or hydrogen; and, Xis chlorine or hydrogen; the ratio of the 3,5-DHPZNA to the secondarystabilizer being in the range from about 5:1 to about 1:5.

For example, a commercially available disphosphite such asbis-(2,4-di-t-butylphenyl)pentaerythritol disphosphite, or distearylpentaerythritol disphosphite, may be used in combination with about thesame amount of the 3,5-DHPZNA; or, a commercially availabletriarylphosphite such as tris-(2,5-di-t-butylphenyl)-phosphite,tris-(2-t-butylphenyl)-phosphite, tris-(2-t-phenylphenyl)-phosphite,tris-[(2-1,1-dimethylpropyl)-phenyl]-phosphite,tris-(2,4-di-t-butylphenyl)-phosphite, and the like; or, a commerciallyavailable benzophenone such as 2-hydroxy-4-n-octoxybenzophenone incombination with about the same amount of the 3,5-DHPZNA; or, acommercially available benzotriazole such as2-(2'-hydroxy-3',5'-di-t-butylphenyl)-5-chlorobenzotriazole (Tinuvin327), 2-(2'-hydroxy-3'-t-butyl-5'-methylphenyl)benzotriazole (Tinuvin326), 2-(2'-hydroxy-5'-methylphenyl)benzotriazole (Tinuvin P),2-(2'-hydroxy-3',5'-dimethylphenyl)-5-chlorobenzotriazole,2-(2'-hydroxy-3',5'-di-t-octylphenyl)benzotriazole (Tinuvin 328), andthe like, in combination with about the same amount of the 3,5-DHPZNA.

It is found that, when the 3,5-DHPZNA is used in combination with one of(a) bis-(alkyl) or bis-(dialkylphenyl)pentaerythritol diphosphite, (b)triarylphosphite, (c) o-hydroxy-benzophenone, and (d) a2-hydroxyphenylbenzotriazole, there is an unexpectedly greater increasein stability of a synthetic resinous material to degradation by uvlight, and very often, also to thermal/oxidative degradation, than onemight be led to expect from the cumulative effectiveness of eachstabilizer used separately. For example, the stability one obtains witha mixture of 0.125 phr of a 3,5-DHPZNA and 0.125 phr of one of thespecific secondary stabilizers, one gets much greater stability thanwith 0.25 phr (the same weight) of a 3,5-DHPZNA. This is most unexpectedbecause the stabilization of such stabilizers is closely correlatable tothe weight (phr) of stabilizer used.

The 3,5-DHPZNAs, such as secondary stabilizers as may be desired, andother compounding ingredients if used, can be admixed with the syntheticresinous material to be stabilized using known mixing techniques andequipment such as internal mixing kettles, a Banbury mixer, a Henschelmixer, a two-roll mill, an extruder mixer, or other standard equipment,to yield a composition which may be extruded, presed, blowmolded or thelike into film, fiber or shaped articles. Usual mixing times andtemperatures can be employed which may be determined with a little trialand error for any particular composition. The objective is to obtainintimate and uniform mixing of the components. A favorable mixingprocedure to use when adding a 3,5-DHPZNA to an organic material iseither to dissolve or suspend the 3,5-DHPZNA in a liquid such asmethylene chloride before adding it, or to add the 3,5-DHPZNA directlyto the synthetic resinous material whether the 3,5-DHPZNA is in the formof a powder or oil, or to extruder-mix the 3,5-DHPZNA and material priorto forming the product.

Many known compoundng ingredients may be used along with the3,5-DHPZNAs, or combinations thereof with secondary stabilizers, in thesynthetic resinous compositions. Such ingredients include lubricantmetal oxides such as zinc, calcium and magnesium oxide, fatty acids suchas stearic and lauric acid, and salts thereof such as cadmium, zinc andsodium stearate and lead oleate; filler such as calcium and magnesiumcarbonate, calcium and barium sulfates, aluminum silicates, asbestos,and the like; plasticizers and extenders such as dialkyl and diarylorganic acids like diisobutyl, diisooctyl, diisodecyl, and dibenzyloleates, stearates, sebacates, azelates, phthalates, and the like; ASTMtype 2 petroleum oils, paraffinic oils, castor oil, tall oil, glycerinand the like.

Other ingredients such as pigments, tackifiers, flame retardants,fungicides, and the like may also be added.

The stabilized resin composition may then be thermoformed by extrusion,injection molding, blow molding and the like, into a wide variety ofarticles ranging from flexible or rigid laminar sheets, self-supportingfilms, filament, and articles of arbitrary shape.

We claim:
 1. AN-(substituted)-1-(piperazinealkyl)-α-(3,5-di-alkyl-4-hydroxyphenyl)-α,α-substitutedacetamide, represented by the structure ##STR26## wherein, R¹, R² and R⁵each represent hydrogen, C₁ -C₁₂ alkyl, phenyl, naphthyl, C₄ -C₁₂cycloalkyl, and alkyl-substituted cycloalkyl, phenyl and naphthyl, eachalkyl substituent being C₁ -C₈, and at least one of R¹ and R² is t-C₄-C₁₂ alkyl;R³ and R₄ independently represent C₁ -C₁₈ alkyl, and C₅ -C₁₂cycloalkyl, phenyl and naphthyl, and, alkyl-substituted cycloalkyl,phenyl and naphthyl, each alkyl substituent being C₁ -C₈, and, whentogether cyclized, R³ with R⁴ may represent C₄ -C₁₂ cycloalkyl, and C₁-C₈ alkyl-substituted cycloalkyl; R⁶, R⁷, R⁸ and R⁹ each represent C₁-C₁₂ alkyl, or, when together cyclized, R⁶ with R⁷, and R⁸ with R⁹, mayrepresent C₄ -C₁₂ cycloalkyl, and C₁ -C₈ alkyl-substituted cycloalkyl;R¹⁰ is selected from the group consisting of hydrogen, C₁ -C₈ alkyl and##STR27## wherein R¹³ represents hydrogen, C₁ -C₁₈ alkyl or alkenyl,phenyl or naphthyl; R¹¹ and R¹² independently represent hydrogen and C₁-C₁₈ alkyl; n is an integer in the range from 1 to about 8; and, Yrepresents H₂ when the diazacycloalkane ring is piperazinyl, and O whenthe diazacycloalkane ring represents piperazin-2-one.
 2. The 3,5-DHPZNAof claim 1 wherein,n is 2 or 3, and Y is oxygen, O; R¹ is C₁ -C₈ alkyl,R² is C₁ -C₅ alkyl, R³ and R⁴ are each C₁ -C₈ alkyl, and together, whencyclized represent cyclohexyl, methylcyclohexyl, cycloheptyl; R⁵ is C₁-C₈ alkyl; and, R¹⁰ is hydrogen or C₁ -C₈ alkyl.
 3. The 3,5-DHPZNA ofclaim 2 wherein,at least one of R¹ and R² is t-butyl, or t-amyl; and, R³and R⁴ are each C₁ -C₄ alkyl.
 4. The 3,5-DHPZNA of claim 1 wherein,n is2 or 3, and Y is hydrogen, H₂ ; R¹ is C₁ -C₈ alkyl, R² is C₁ -C₅ alkyl,R³ and R⁴ are each C₁ -C₈ alkyl, and together, when cyclized representcyclohexyl, methylcyclohexyl, cycloheptyl; R⁵ is C₁ -C₈ alkyl; and, R¹⁰is hydrogen or C₁ -C₈ alkyl.
 5. The 3,5-DHPZNA of claim 4 wherein,atleast one of R¹ and R² is t-butyl, or t-amyl; and, R³ and R⁴ are each C₁-C₄ alkyl.
 6. The 3,5-DHPZNA of claim 2 selected from the groupconsisting of(1)N-isopropyl-N-[2-(2-keto-3,3,5,5-tetramethyl)-1-piperazinyl)ethyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methyl-propanamide(2)N-[1-(2-keto-3,3,5,5-tetramethyl-1-piperaznyl-2-methyl-2-propyl]-2-(3,5-di-t-butyl-4-hydroxypheny)-2-methyl-propanamide(3)N-[1-(2-keto-3,5,5-trimethyl-3-ethyl-1-piperazinyl-2-methyl-2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methyl-butanamide(4)N-[1-(2-keto-3,3-pentamethylene-5,5-dimethyl-1-piperazinyl)-2-methyl-2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethyleneacetamide (5) N-[1-(2-keto-3,3,5,5-tetramethyl-1-piperazinyl-2-methyl2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethyleneacetamide (6) N-cyclohexyl-N-[2-(2-keto-3,3,5-tetramethyl-1-piperazinylethyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethylene acetamide(7) N-cyclohexyl-N-[3-(2-keto-3,3,5,5-tetramethyl-1-piperazinylpropyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethylene acetamide(8)N-cyclohexyl-N-[3-(2-keto-3,3,5,5-tetramethyl-1-piperazinyl-propyl]-2-(3,5,-di-t-butyl-4-hydroxyphenyl)-2-methylpropanamide (9)N-cyclohexyl-N-[3-(2-keto-3,3,5,5-tetramethyl-1-piperazinyl-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methylbutanamide.
 7. The 3,5-DHPZNA of claim 4 selected from the groupconsisting of(1)N-isopropyl-N-[2-(3,3,5,5-tetramethyl-1-piperazinyl)ethyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methyl-propanamide(2)N-[1-(3,3,5,5-tetramethyl-1-piperazinyl-2-methyl-2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methylpropanamide(3)N-[1-(3,5,5-trimethyl-3-ethyl-1-piperazinyl-2-methyl-2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methylbutanamide(4)N-[1-(3,3-pentamethylene-5,5-dimethyl-1-piperazinyl)-2-methyl-2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethyleneacetamide (5) N-[1-(3,3,5,5-tetramethyl-1-piperazinyl-2-methyl2-propyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethyleneacetamide (6) N-cyclohexyl-N-[2-(3,3,5,5-tetramethyl-1-piperazinylethyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethylene acetamide(7) N-cyclohexyl-N-[3-(3,3,5,5-tetramethyl-1-piperazinylpropyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2,2-pentamethylene acetamide(8)N-cyclohexyl-N-[3-(3,3,5,5-tetramethyl-1-piperazinylpropyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methylpropanamide (9)N-cyclohexyl-N-[3-(3,3,5,5-tetramethyl-1-piperazinylpropyl]-2-(3,5-di-t-butyl-4-hydroxyphenyl)-2-methylbutanamide.
 8. A stabilized composition of matter comprising an organicmaterial subject to degradation, in which material is dispersed from0.05 to 5 parts per hundred parts by weight of the material, of aN-(substituted)-1-(piperazinealkyl)-α-(3,5-dialkyl-4-hydroxyphenyl)-α,α-substitutedacetamide, represented by the structure ##STR28## wherein, R¹, R² and R⁵each represent hydrogen, C₁ -C₁₂ alkyl, phenyl, naphthyl, C₄ -C₁₂cycloalkyl, and, alkyl-substituted cycloalkyl, phenyl and naphthyl, eachalkyl substituent being C₁ -C₈, and at least one of R¹ and R² is t-C₄-C₁₂ alkyl;R³ and R⁴ independently represent C₁ -C₁₈ alkyl, and C₅ -C₁₂cycloalkyl, phenyl and naphthyl, and, alkyl-substituted cycloalkyl,phenyl and naphthyl, each alkyl substituent being C₁ -C₈, and, whentogether cyclized, R³ with R⁴ may represent C₄ -C₁₂ cycloalkyl, and C₁-C₈ alkyl-substituted cycloalkyl; R⁶, R⁷, R⁸ and R⁹ each represent C₁-C₁₂ alkyl, or, when together cyclized, R⁶ with R⁷, and R⁸ with R⁹, mayrepresent C₄ -C₁₂ cycloalkyl, and C₁ -C₈ alkyl-substituted cycloalkyl;R¹⁰ is selected from the group consisting of hydrogen, C₁ -C₈ alkyl and##STR29## wherein R¹³ represents hydrogen, C₁ -C₁₈ alkyl or alkenyl,phenyl or naphthyl; R¹¹ and R¹² independently represent hydrogen and C₁-C₁₈ alkyl; n is an integer in the range from 1 to about 8; and, Yrepresents H₂ when the diazacycloalkene ring is piperazinyl, and O whenthe diazacycloalkane ring represents piperazin-2-one.
 9. The stabilizedcomposition of matter of claim 8 wherein said 3,5-DHPZNA ischaracterized by,n is 2 or 3, and Y is oxygen, O; R¹ is C₁ -C₈ alkyl, R²is C₁ -C₅ alkyl, R³ and R⁴ are each C₁ -C₈ alkyl, and together, whencyclized represent cyclohexyl, methylcyclohexyl, cycloheptyl; R⁵ is C₁-C₈ alkyl; and, R¹⁰ is hydrogen or C₁ -C₈ alkyl.
 10. A method ofstabilizing a synthetic resinous material derived from a singlyunsaturated acyclic hydrocarbon, or mixtures of copolymers thereof,during processing said material, which method comprises incorporating insaid material a mixture comprising(i) from 0.05 to 5 phr of aN-(substituted)-1-(piperazinealkyl)-α-(3,5-dialkyl-4-hydroxyphenyl)-α,α-substitutedacetamide, represented by the structure ##STR30## wherein, R¹, R² and R⁵each represent hydrogen, C₁ -C₁₂ alkyl, phenyl, naphthyl, C₄ -C₁₂cycloalkyl, and, alkyl-substituted cycloalkyl, phenyl and naphthyl, eachalkyl substituent being C₁ -C₈, and at least one of R¹ and R² is t-C₄-C₁₂ alkyl; R³ and R⁴ independently represent C₁ -C₁₈ alkyl, and C₅ -C₁₂cycloalkyl, phenyl and naphthyl, and, alkyl-substituted cycloalkyl,phenyl and naphthyl, each alkyl substituent being C₁ -C₈, and, whentogether cyclized, R³ with R⁴ may represent C₄ -C₁₂ cycloalkyl, and C₁-C₈ alkyl-substituted cycloalkyl; R⁶, R⁷, R⁸ and R⁹ each represent C₁-C₁₂ alkyl, or, when together cyclized, R⁶ with R⁷, and R⁸ with R⁹, mayrepresent C₄ -C₁₂ cycloalkyl, and C₁ -C₈ alkyl-substituted cycloalkyl;R¹⁰ is selected from the group consisting of hydrogen, C₁ -C₈ alkyl and##STR31## wherein R¹³ represents hydrogen, C₁ -C₁₈ alkyl or alkenyl,phenyl or naphthyl; R¹¹ and R¹² independently represent hydrogen and C₁-C₁₈ alkyl; n is an integer in the range from 1 to about 8; and, Yrepresents H₂ when the diazacycloalkane ring is piperazinyl, and O whenthe diazacycloalkane ring represents piperazin-2-one; (ii) from 0.05 toabout 5 phr of another stabilizer selected from the group consisting ofa (a) bis-(dialkylphenyl)pentaerythritol diphosphite, (b)triarylphosphite, (c) o-hydroxy-benzophenone, and (d) a2-hydroxyphenylbenzotriazole,said diphosphite represented by thestructure ##STR32## wherein R¹⁴ is C₃ -C₂₄ alkyl, or di-(C₃-C₉)alkylphenyl; said triarylphosphite represented by the structure##STR33## wherein R¹² represents t-butyl, 1,1-dimethylpropyl, cyclohexylor phenyl, and one of R¹³ and R¹⁴ is hydrogen and the other is hydrogen,methyl, t-butyl, 1,1-dimethylpropyl, cyclohexyl or phenyl; saido-hydroxy-benzophenone represented by the structure ##STR34## whereinR¹⁸ is C₁ -C₂₄ alkyl, and, said 2-hydroxyphenylbenzotriazole representedby the structure, ##STR35## wherein R¹⁹ is lower alkyl or halogen(preferably chlorine); R²⁰ is lower alkyl, halogen (preferablychlorine), or hydrogen; and, X is chlorine or hydrogen; the ratio of the3,5-DHPZNA to the secondary stabilizer being in the range from about 5:1to about 1:5.
 11. The method of claim 10 for stabilizing a syntheticresinous material wherein said 3,5-DHPZNA is characterized by,n is 2 or3, and Y is oxygen, O; R¹ is C₁ -C₈ alkyl, R² is C₁ -C₅ alkyl, R³ and R⁴are each C₁ -C₈ alkyl, and together, when cyclized represent cyclohexyl,methylcyclohexyl, cycloheptyl; R⁵ is C₁ -C₈ alkyl; and, R¹⁰ is hydrogenor C₁ -C₈ alkyl.
 12. A process for preparing aN-(substituted)-1-(piperazinealkyl)-α-(3,5-dialkyl-4-hydroxyphenyl)-α,α-substitutedacetamide, represented by the structure ##STR36## wherein, R¹, R² and R⁵each represnt hydrogen, C₁ -C₁₂ alkyl, phenyl, naphthyl, C₄ -C₁₂cycloalkyl, and, alkyl-substituted cycloalkyl, phenyl and naphthyl, eachalkyl substituent being C₁ -C₈, and at least one of R¹ and R² is t-C₄-C₁₂ alkyl;R³ and R⁴ independently represent C₁ -C₁₈ alkyl, and C₅ -C₁₂cycloalkyl, phenyl and naphthyl, and, alkyl-substituted cycloalkyl,phenyl and naphthyl, each alkyl substituent being C₁ -C₈, and, whentogether cyclized, R³ with R⁴ may represent C₄ -C₁₂ cycloalkyl, and C₁-C₈ alkyl-substituted cycloalkyl; R⁶, R⁷, R⁸ and R⁹ each represent C₁-C₁₂ alkyl, or, when together cyclized, R⁶ with R⁷, and R⁸ with R₉, mayrepresent C₄ -C₁₂ cycloalkyl, and C₁ -C₈ alkyl-substituted cycloalkyl;R¹⁰ is selected from the group consisting of hydrogen, C₁ -C₈ alkyl and##STR37## wherein R¹³ represents hydrogen, C₁ -C₁₈ alkyl or alkenyl,phenyl or naphthyl; R¹¹ and R¹² independently represent hydrogen and C₁-C₁₈ alkyl; n is an integer in the range from 1 to about 8; and, Yrepresents H₂ when the diazacycloalkane ring is piperazinyl, and O whenthe diazacycloalkane ring represents piperazin-2-one;said processcomprising, reacting (i) a 2,6-dialkylphenol represented by thestructure ##STR38## wherein, R¹ and R² have the same connotation ashereinabove, with (ii) an excess over stoichiometric of a ketoneselected from the group consisting of C₁ -C₈ dialkyl ketones, C₅ -C₈cycloalkanones, C₁ -C₈ alkyl-cycloalkanes, and C₁ -C₈ alkylphenylketones, and, (iii) a haloform selected from the group consisting ofchloroform and bromoform, and, (iv) a 4-amino-polysubstituted piperazinerepresented by the structure ##STR39## wherein Y, R⁵, R⁶, R⁷, R⁸, R⁹,R¹⁰ R¹¹ and R¹² have the same connotation as that given hereinbefore, inthe presence of an alkali metal hydroxide.
 13. The process of claim 12wherein said 3,5-DHPZNA is characterized by,n is 2 or 3, and Y isoxygen, O; R¹ is C₁ -C₈ alkyl, R² is C₁ -C₅ alkyl, R³ and R⁴ are each C₁-C₈ alkyl, and together, when cyclized represent cyclohexyl,methylcyclohexyl, cycloheptyl; R⁵ is C₁ -C₈ alkyl; and, R¹⁰ is hydrogenor C₁ -C₈ alkyl.